JPH074666B2 - Welding line copying control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention oscillates a welding torch to detect an electrical change associated with changes in the arc length and the wire protrusion length, and imitates the welding line. It relates to a control method.

[Prior Art] Conventionally, a welding line tracing that causes a welding torch to follow a welding line by a detection signal of an arc sensor that oscillates the welding torch and detects electrical changes caused by changes in the arc length and the wire protrusion length A control method is used.

In the case of horizontal fillet welding, this conventional arc sensor has obtained relatively good results in welding at a relatively low welding speed of about 120 cm / min. Further, in the case of horizontal fillet welding, a thin plate up to a thickness of about 2.0 mm can be practically used.

Usually, the penetration depth of a work piece of a predetermined plate thickness changes depending on the welding current value, the welding speed and the oscillating speed, and this oscillating speed is the oscillating frequency, the oscillating width, the welding speed, the oscillating waveform, and the oscillating stop time. Determined by variables. Below, in order to simplify the explanation,
A case will be described in which the oscillating frequency that most affects the oscillating speed is changed and the other variables are set to predetermined substantially constant values.

Thus, when the welding speed is low, the oscillating frequency of the welding torch is a low frequency of about 0.5 to 5 Hz. Regarding the conventional example at this time, referring to FIG. 2 and FIG. The relationship of the welding current value with respect to each oscillating position when the WT is oscillating between the left workpiece Wl and the right workpiece Wr will be described. FIG. 2 (B) shows
In the case where the center position C of the oscillate (hereinafter referred to as the oscillate center) and the welding line W ₀ coincide, A ₀ and A ₁ are the lengths of the consumable electrodes protruding from the tip of the welding torch in the figure. (Hereinafter, referred to as wire protrusion length), and B ₀ represents a distance (hereinafter, referred to as arc length) between the tip of the consumable electrode (hereinafter, referred to as wire) and the surface of the workpiece in the wire tip direction. When the welding torch WT is at the left end L ₀ of the oscillating width, the protrusion length is A ₁ , the arc length is B ₀ , and the welding torch WT is at the oscillating center C from the left end L ₀ , that is, the position of the welding line W ₀ . Until reaching, as mentioned above,
When the oscillating frequency is low frequency, the welding current value rapidly increases due to the self-control action of the welding power source of constant voltage characteristic, the melting rate increases, and the arc length becomes approximately constant value B _0. The wire protrusion length gradually increases from A ₁ to A ₀ . As the wire protrusion length increases, the average value I (vertical axis) of the welding current decreases from I ₁ to I ₀ with respect to the oscillating position P (horizontal axis), as shown in FIG. Welding torch WT
Is moving from the oscillating center C to the right end R ₀ , contrary to the operation described above, the wire protrusion length is reduced from A ₀ to A ₁ while the arc length B ₀ remains constant and the welding current value is also Increase from I ₀ to I ₁ . Therefore, when the oscillating center C and the welding line W ₀ match (hereinafter, “when there is no positional deviation”)
That is, the welding current values I on both sides of the welding line W ₀ are bilaterally symmetric and have the same current value in both the oscillation reciprocation. Further, FIG. 6C and FIG.
The relationship of the welding current value I and the oscillating position P (vertical axis) with respect to the progress of (horizontal axis) is shown. FIG. 3 shows the case where the oscillating center C and the welding line W ₀ are deviated (hereinafter referred to as “when there is a positional deviation”), and the welding torch WT exceeds the oscillating center C from the left end L ₁ of the oscillating. While oscillating to the right end R ₁ of the arc length B ₀ as in the operation of FIG.
Is a constant value, the wire protrusion length is from A ₃ to A
After increasing to ₀ (welding line), it further decreases from A ₀ to over A ₄ (oscillate center) to A ₅ . Therefore, when there is a positional deviation, the welding current values I on both sides of the welding line W ₀ are left-right asymmetrical, but the same current value is obtained in both oscillating reciprocations. Further, FIGS. 7C and 7D respectively show the relationship between the welding current value I and the oscillating position P (vertical axis) with respect to the passage of time t (horizontal axis).

The above is the description using FIG. 2 and FIG. 3 in the case of the conventional low frequency oscillation, and next, the relationship with the known empirical formula will be described. Generally, the wire melting rate Vm of arc welding is represented by the following equation.

Vm = a ・ Ia + b ・ A ・ (Ia) ² (1) However, 1a: average value of welding current A: wire protrusion length a, b, c: constant Arc length B ₀ is almost constant in low frequency oscillation. So
The wire melting speed Vm and the wire feeding speed Vf become equal,
The following equation holds.

Vm = Vf = g However, g is a constant …… (2) From formulas (1) and (2), a ・ Ia + b ・ A ・ (Ia) ² = Vm = Vf = g …… (3) Formula (3) When differentiated by time t and rearranged, a · dIa + b {(Ia) ² · dA + 2A · Ia · dIa} = 0 ……
(4) When the distance between the tip of the welding torch WT and the surface of the workpiece in the wire tip direction (hereinafter referred to as the torch tip distance) is D, D = B ₀ + A (5) Since the arc length B ₀ has a smaller value than the wire protrusion length A and is substantially constant, D≈A, and therefore A in the equation (3)
Substituting D into and rearranging yields the following equation.

Since the equation (6) does not include the term of time, the welding current value is determined by the torch tip distance D determined by the oscillating position.
Ia is determined. That is, when the torch tip distance D that the welding torch passes while moving from the left end to the right end (right direction) of the oscillating width and the torch tip distance D that passes while moving from the right end to the left end (left direction) have the same value. Irrespective of whether the welding torch is moving to the left or to the right, or in the left half position or the right half position of the welding line, the welding current value is the same. Shows. This means the same as the operation of FIGS. 2 and 3 described above. Therefore, the prior art is based on the above-mentioned FIG. 2 and FIG.
The welding line is recognized by comparing the integral value of the welding current in the right half of the oscillate with the integral value of the welding current in the left half based on the operation in the figure or the equation (6).

The welding line is recognized by comparing the peak value of the welding current at the specified position in the right half of the oscillate with the peak value of the welding current at the specified position in the left half.

Recognize the position of the minimum current value during oscillating as the welding line.

In addition, the welding line is recognized by the above modified examples or combinations.

Is being done.

As described above, in the conventional low-frequency oscillation of 0.2 to 5 Hz, the change in the melting rate of the wire follows the change in the position of the oscillation and the arc length B ₀ can be maintained substantially constant. Since the welding current value follows the change of A or the change of the torch distance and changes in the relationship shown in FIG. 2 and FIG. 3 or the expression (6), a good welding line profile is obtained by the above control methods (1) to (3). I was in control.

However, this control method has been gradually expanded to horizontal fillet welding of thin plates of about 2.0 mm, but since the welding speed becomes higher at a thin plate of about 1.6 mm, oscillating If the frequency is around 0.2-5Hz, the
The meandering of the welding bead due to the oscillating was conspicuous, and in order to prevent it, it became necessary to raise the oscillating frequency to 5 Hz or higher. When the oscillating frequency reaches a frequency of about 5 Hz, as shown in FIG. 4, the oscillating position changes rapidly, so the wire melting speed Vm corresponding to the change in the torch tip distance A + B is delayed and the arc length B increases. Fluctuates, and changes in the welding current value I cannot apply the equations shown in FIGS. 2 and 3 or (6).

That is, in FIG. 4 (B), when there is no displacement, the welding torch WT is oscillating from the left end L ₀ to the right end R _0.
As it moves toward, the wire tip Wa draws a curved locus as shown in FIG. The reason for drawing such a locus is that when the oscillating frequency becomes a frequency of about 5 Hz, when the torch tip distance A + B gradually increases, the decrease in the wire melting speed Vm follows the change in the torch tip distance A + B due to the change in the oscillating position. Therefore, the arc length B cannot be maintained constant, and as shown in FIG. 4 (B), the arc length increases from B _{0 at the} left end to B ₂ and passes through the oscillating center C. Then, it decreases to B ₃ and then increases to B ₀ at the right end. Along with this, the welding current value, as shown in FIG. (A), than I ₆ when the oscillating center C decreases from I _5, was further reduced to I _7, increasing to the right edge of I ₅ To do.

Next, when there is a positional deviation, the wire tip Wa draws a locus of a curve as shown in FIG. 5 (B) as the welding torch WT oscillates. ) Is known to draw a locus.

In this way, when the oscillating frequency approaches 5 Hz, the conventional method of comparing the integral value, the peak value, the minimum value of one cycle, etc. of the welding current value of the right half and the left half of the oscillate is It is becoming difficult to apply it to practical use because no significant change corresponding to the deviation can be obtained. In order to improve this point, the difference between the minimum value of the welding current during oscillating to the right and the current value at the right end, and the difference between the minimum value of the welding current during oscillating to the left direction and the current value at the left end. A method of comparing and recognizing the welding line, or an integral value of the welding current between the right half and the left half during oscillating to the right, and an integral value of the welding current between the right half and the left half during oscillating to the left half. A method of recognizing the welding line by comparing the above has been devised. However, these improvements were also obtained by detecting since the oscillation frequency was up to a low frequency of about 5 Hz, and at higher frequencies, the locus of the welding current value with respect to the oscillation position further changed, as will be described later. Since the difference between the comparison values is small, it is becoming difficult to detect the welding line with high accuracy.

[Problems to be Solved by the Invention] A conventional welding line tracing control method in an oscillation at a low frequency of about 0.5 to 5 Hz is achieved by applying the operation shown in FIG. 2 or 3 or the expression (6). Since it is assumed that the arc length B ₀ is constant regardless of the position, if the oscillating position, that is, the torch tip distance is the same regardless of the right oscillating or left oscillating, the welding current value is the same. This is a control method based on the above or a control method improved from it.

Therefore, with the conventional control method, the maximum welding speed is up to 120 cm / min for horizontal fillet welding and 8 for overlap fillet welding.
It is up to 0 cm / min, and the minimum plate thickness is horizontal fillet welding.
It was 2.0 mm and 3.2 mm in overlap fillet welding. Further, in the conventional control method, in vertical downward welding, it is difficult to practically use because the drooping speed of the molten metal is faster than the welding speed, and it is shared between spray arc welding and short arc welding. It was not possible, and it had to use a separate control method. Therefore, it has become impossible to meet the recent demand for automation of high-speed welding and vertical welding of thin plates of various parts of automobiles.

[Means for Solving the Problems] The present invention relates to an oscillating position in each range from an intermediate frequency of 5 to 7 Hz to a high frequency of 7 to 10 Hz as the welding speed increases. That is, the relationship between the oscillating position and the welding current value is considered in consideration of the delay of the change of the wire melting speed corresponding to the change of the torch tip distance and the transient phenomenon such as the delay of the change of the welding current value output from the welding power source. Based on this, a scanning control method for detecting a deviation between the oscillating center C and the welding line W ₀ is proposed.

According to a first aspect of the present application, welding line tracing control is performed in which a welding torch is oscillated to detect an electrical change caused by a change in arc length and wire protrusion length, and the welding torch is made to follow a welding line by the detection signal. In the method, a first comparison signal for comparing the detection signal detected when the welding torch is traveling to the right in the right half of the oscillating width with the detection signal detected when traveling to the left, and A second comparison signal for comparing the detection signal detected when the welding torch is traveling leftward in the left half of the oscillating width with the detection signal detected when traveling rightward is calculated. The invention relates to a welding line tracing control method for moving the oscillating center of the welding torch in a direction in which the difference between the first comparison signal and the second comparison signal becomes smaller.

According to a second aspect of the present application, welding line tracing control is performed in which the welding torch is oscillated to detect an electrical change caused by a change in arc length and wire protrusion length, and the welding torch is made to follow the welding line by the detection signal. In the method, a first comparison is made between the detection signal detected at the right end of the oscillation when the welding torch is traveling to the right of the oscillating width and the detection signal detected at the center of the oscillation when traveling to the left.
And a detection signal detected at the left end of the oscillation when the welding torch is traveling to the left of the oscillating width and a detection signal detected at the center of the oscillation when traveling to the right. Comparing with the comparison signal, the first
The invention relates to a welding line tracing control method in which the oscillating center of the welding torch is moved in the direction in which the difference between the comparison signal and the second comparison signal becomes smaller.

[Operation] Hereinafter, a transient phenomenon of the characteristics of the welding power source and the arc that influences the change in the arc length, which is the premise of the present invention, will be examined.

Characteristics of welding power source Ea ＝ E ₀ -R ・ Ia-L (dIa / dt) (7) R: resistance value of circuit L: inductance value of circuit (including delay element of control system) E ₀ : welding power source No-load voltage average value Ea: Welding voltage average value Arc characteristics Ea = E ₁ + αIa + β ・ B (8) B is arc length E ₁ , α, β are constants Wire melting rate characteristics From the equation (5), Vm = Vf− (dA / dt) = Vf + (dB / dt) − (dD / dt) (9) Equation (1), Equation (5) and Equation (7) to (9) K ₂ from the equation ^{(d 2 Ia / dt 2)} + (K 1 + b · K 2 · I 2 a) (dIa / dt) + {a + b (D-K 0 + K 1 Ia) Ia} Ia = Vf- (dD / dt) (10) where K ₀ = (E ₀ −E ₁ ) / β, K ₁ = (R + α) / β, K ₂ = L / β Using the equation (10) obtained as above The results of the simulation are shown in FIGS. 6 to 9. FIGS. 6 to 9 show the oscillating position P (horizontal axis) and welding current of the welding torch at oscillating frequencies of ultra-low frequency 0.5 to 2 Hz, low frequency 2 to 5 Hz, intermediate frequency 5 to 7 Hz and high frequency 7 to 10 Hz, respectively. It is a figure which shows the relationship with the average value I (vertical axis) of.

Therefore, based on FIGS. 7 to 9, the present invention has proposed a control method for surely detecting the deviation between the oscillating center C and the welding line W ₀ and causing the welding torch to follow the welding line. 7th
In FIGS. 9 to 9, when there is no positional deviation, there is a minimum value in the average value of the welding current, and when the positional deviation is small, a curve like that shown in FIG.
There is a position showing the minimum welding current value. However, when the positional deviation becomes large, the position showing the minimum current value of the welding current does not appear during oscillating. Furthermore, when the oscillating frequency becomes a high frequency of 7-10Hz, 2
The direction of the locus of the welding current value is opposite to the case of the low frequency of ~ 5Hz.

An example of the present invention will be described based on the above examination results.

[Examples] (1) Example of claim 1 Example 1 Example 1 is the first example with respect to claim 1, wherein the welding torch WT is oscillated and the arc length is increased. Also, in the welding line tracing control method that detects the change in welding current due to the change in wire protrusion length and causes the welding torch to follow the welding line W ₀ by the detection signal, the welding torch advances to the right in the right half of the oscillation width. The ratio ΣRr / ΣRl of the integral value ΣRr (first detection signal) of the welding current detected while the vehicle is moving to the integral value ΣRl (second detection signal) of the welding current detected when traveling to the left The first comparison signal R ₁ is calculated, and then the integrated value ΣRl (third detection signal) of the welding current detected when the welding torch is traveling leftward in the left half of the oscillating width and rightward. Integral value ΣLr of welding current detected while moving (fourth detection signal) Second calculating a comparison signal L ₁ ratio ΣRL / ΣLr, these difference signal J ₁ = R ₁ -L ₁
This is a welding line tracing control method in which the oscillating center of the welding torch is moved in the direction in which becomes smaller.

Next, regarding the relationship between the oscillating position and the welding current value when the oscillating frequency is a low frequency of 2 to 5 Hz, an intermediate frequency of 5 to 7 Hz and a high frequency of 7 to 10 Hz, FIG. 5 and FIG. 7 to FIG. To explain. When there is no displacement in any frequency, the first comparison signal R and the second comparison signal L coincide with each other and R = L, and the oscillating center does not move. Is omitted.

Low frequency and intermediate frequency oscillation In FIG. 7 (A), R ₁ = ΣRr / ΣRl> 1, L ₁ = ΣLl / Σ
Since Lr <1, R ₁ −L ₁ > 0, and the oscillating center C is shifted to the right with respect to the welding line W ₀ , so the oscillating center is moved to the left. In the figure (C), contrary to the figure (A), R ₁ = ΣRr / ΣRl <1, L ₁ = ΣLl / ΣLr> 1
Therefore, R ₁ −L ₁ <0, and the oscillating center C is displaced to the left with respect to the welding line W ₀ , so the oscillating center is moved to the right.

In FIG. 8 (A), R ₁ = ΣRr / ΣRl≈1, L ₁ = ΣLl / Σ
Since Lr <1, R ₁ −L ₁ > 0, which is the same as in FIG. 7A. Further, in FIG. 8 (C), R ₁ =
Since ΣRr / ΣRl <1, L ₁ = ΣLl / ΣLr≈1, R ₁ −L ₁ <
It becomes 0, and is the same as that in FIG. 7 (C).

High Frequency Oscillation In FIG. 9 (A), R ₁ = ΣRr / ΣRl <1, L ₁ = ΣLl / Σ
Since Lr> 1, R ₁ −L ₁ <0, and the relationship of FIG.
Although the sign is opposite to R ₁ -L ₁ > 0, since the oscillating center C is shifted to the right with respect to the welding line W ₀ , the oscillating center is moved to the left. In the same figure (C), R ₁
-L ₁ > 0, which is the opposite sign of R ₁ -L ₁ <0 in FIG. 7 (C), but since the oscillating center C is shifted to the left with respect to the welding line W ₀ , oscillating Move the center to the right.

When the positional deviation is small When the positional deviation is small, the locus of welding current in FIG. 7 (A) draws the locus shown in FIG. 5 (A). Also in this case, R ₁ = ΣRr / ΣRl> 1 and L ₁ = ΣLl / ΣLr> 1.
Since it is> Il, R ₁ −L ₁ > 0, which is the same as FIG. 7 (A). Even when the positional deviation in the opposite direction is small in FIG. 5 (C), R ₁ −L ₁ is the same as in FIG. 7 (C).
<0. In each embodiment described later, when the positional deviation is small, the description is omitted because it is the same as when the normal positional deviation is large.

Second Embodiment The second embodiment is a second embodiment with respect to the first claim, and in the first embodiment, the first detection signal Σ
The first comparison signal R ₂ of the difference (ΣRr−ΣRl) between Rr and the second detection signal ΣRl is obtained, and then the difference (ΣLl−ΣLr) between the third detection signal ΣLl and the fourth detection signal ΣLr. ) Second comparison signal L ₂
Is obtained and the signal J ₂ = R ₂ −L _{2 of} these differences is moved to the minimum value, and the oscillating center of the welding torch is moved.

Similar to the first embodiment, description will be made with reference to FIGS. 7 to 9.

Low frequency and intermediate frequency oscillation In FIG. 7 (A), R ₂ = ΣRr−ΣRl> 0, L ₂ = ΣLl−
Since ΣLr <0, R ₂ −L ₂ > 0, and the same as in the first embodiment. In the same figure (C), R ₂ = ΣRr−
Since ΣRl <0, L ₂ = ΣLl−ΣLr> 0, R ₂ −L ₂ <0, and the same as in the first embodiment.

In FIG. 8 (A), R ₂ = ΣRr−ΣRl≈0, L ₂ = ΣLl−
Since ΣLr <0, R ₂ −L ₂ > 0, which is the same as in FIG. 7A. Further, in FIG. 8 (C), R ₁ =
Since ΣRr−ΣRl <0, L ₂ = ΣLl−ΣLr≈0, R ₁ −L ₁
<0, which is the same as in FIG. 7 (C).

High-frequency oscillator In FIG. 9 (A), R ₂ = ΣRr−ΣRl <0, L ₂ = ΣLl−Σ
Since Lr> 0, R ₂ −L ₂ <0, and the same as in the first embodiment. In the same figure (C), R ₂ = ΣRr−Σ
Since Rl> 0, L ₂ = ΣLl−ΣLr <0, R ₂ −L ₂ > 0, and the same as in the first embodiment.

Example 3 The third example is the third example with respect to the first aspect of the present invention, in which the welding torch WT is oscillated to change the welding current due to changes in the arc length and the wire protrusion length. In the welding line tracing control method in which the welding torch is made to follow the welding line W _{0 according} to the detected signal, a predetermined position (for example, an intermediate position) when the welding torch is traveling rightward in the right half of the oscillating width ) Of the welding current value Rr (first detection signal) and the welding current value Rl (second detection signal) detected at the above predetermined position when traveling to the left
The first comparison signal R ₃ of Rr / Rl is calculated, and then the welding current detected at a predetermined position (for example, an intermediate position) when the welding torch is traveling leftward in the left half of the oscillating width. value
The ratio Ll / Lr of Ll (third detection signal) and welding current value Lr (fourth detection signal) detected at the predetermined position (for example, intermediate position) when traveling to the right 2 comparison signal L
_This is a welding line tracing control method in which ₃ is calculated and the oscillating center of the welding torch is moved in the direction in which the difference signal J ₃ = R ₃ −L ₃ becomes smaller.

Similar to the first embodiment, description will be made with reference to FIGS. 7 to 9.

Low Frequency and Intermediate Frequency Oscillation In FIG. 7 (A), R ₃ = Rr / Rl> 1 and L ₃ = Ll / Lr <1. Therefore, R ₃ −L ₃ > 0. Similar to the example. In the same figure (C), R ₃ = Rr / Rl <1, L ₃ = Ll /
Lr> 1 and R ₃ −L ₃ <0, which is the same as in the first embodiment.

In FIG. 8 (A) and FIG. 8 (C), R ₃ ≈0,
L ₃ ≈0, but the same as above.

High Frequency Oscillation In FIG. 9 (A), R ₃ = Rr / Rl <1, L ₃ = Ll / Lr> 1, so R ₃ −L ₃ <0, and the same as in the first embodiment. . In the same figure (C), R ₃ = Rr / Rl> 1, L ₃ = Ll / Lr
Since it is <1, R ₃ −L ₃ > 0, and the same as in the first embodiment.

Fourth Embodiment The fourth embodiment is the fourth embodiment with respect to the first claim, and in the third embodiment, the first detection signal Rr is used.
The first comparison signal of the difference (Rr-Rl) between the second detection signal Rl and
R ₄ is obtained, and then the third detection signal Ll and the fourth detection signal Lr
The second comparison signal L ₄ of the difference (Ll−Lr) with the welding line for moving the oscillating center of the welding torch so that the signal J ₄ = R ₄ −L _{4 of} these differences becomes the minimum value. This is a copying control method.

Similar to the first embodiment, description will be made with reference to FIGS. 7 to 9.

Low Frequency and Intermediate Frequency Oscillation In FIG. 7 (A), R ₄ = Rr-Rl> 0, L ₄ = Ll-Lr <0
Therefore, R ₄ −L ₄ > 0, which is the same as in the first embodiment. In the figure (C), R ₄ = Rr-Rl <0, L ₄ =
Since Ll−Lr> 0, R ₄ −L ₄ <0, and the first
It is similar to the embodiment of.

In FIG. 8 (A) and FIG. 8 (C), R ₄ ≈0,
L ₄ ≈0, but the same as above.

High Frequency Oscillation In FIG. 9 (A), R ₄ = Rr−Rl <0, L ₄ = Ll−Lr> 0, so R ₄ −L ₄ <0, and the same as in the first embodiment. . In the same figure (C), R ₄ = Rr-Rl> 0, L ₄ = Ll
Since −Lr <0, R ₄ −L ₄ > 0, which is the same as in the first embodiment.

Embodiment 5 The fifth embodiment is the fifth embodiment with respect to the first claim, and as shown in FIG. 6, when the oscillating frequency is low frequency of 2 to 5 Hz and 7 to 10 Hz. At high frequencies, the locus of the welding current value is in the reverse rotation direction with respect to the oscillating direction. That is, at the low frequency of 2 to 5 Hz, the right end of the oscillate rotates clockwise, and the left end of the oscillate rotates counterclockwise (hereinafter referred to as forward rotation), while at the high frequency of 7 to 10 Hz, On the contrary, the right end of the oscillate turns counterclockwise, and the left end of the oscillate turns right (hereinafter referred to as reverse rotation).

Therefore, in this embodiment, the oscillation frequency is set to the low frequency 2
.About.5 Hz to high frequencies 7 to 10 Hz, and in the vicinity of 6 Hz, the first comparison signal R and the second comparison signal L in the first to fourth embodiments described above. Alternatively, the polarity of the difference signal may be switched.

The reason why the locus of the welding current value is in the reverse rotation direction when the oscillating frequency becomes a high frequency of 7 to 10 Hz is that the inductance of the circuit of L (dIa / dt) in the equation of the characteristics of the welding power source of equation (7) Changes the welding current with time
This is because it becomes impossible to follow the change in the wire melting rate characteristic of the equation (9).

That is, in FIG. 10 (A), the relationship between the oscillating position and the position of the object to be welded when the oscillating center C of the welding torch and the welding line W ₀ match (when there is no displacement) FIG. 6B is a diagram showing an oscillating position P with respect to time t, and FIGS. 7C to 7F are oscillating positions at oscillating frequencies of 0.5 Hz, 5 Hz, 7 Hz and 10 Hz, respectively. It is a diagram showing a locus of a change in the welding current value I with respect to P, and the same graphs (G) to (J) show the elapsed time t.
The change of the welding current value I with respect to is shown. When the oscillating frequency is an ultra-low frequency of 0.5 Hz, for example, when the oscillating position shown in FIG. (B) is at the rightmost oscillating width position R ₀ , the welding current value shown in FIG. _{5 and} both are in phase.

The oscillating frequency is 5Hz, which is higher than the very low frequency of 0.5Hz.
When the frequency becomes low, the change in the wire melting rate cannot follow the change in the torch tip distance, and the arc length changes and the welding current value changes, as described in FIGS. 4 (A) and (B). Therefore, as shown in FIG. 10 (H), the maximum position I ₅ of the welding current value is a position (advanced position) that is faster than the maximum oscillating position R ₀ of the rightmost oscillating width by θ ₁ . Therefore, when the same figure (B) and the same figure (H) are combined and the component of the time t is deleted, the locus of the welding current with respect to the oscillating position is the rotation direction (forward rotation) shown in the same figure (D)
Becomes

Next, when the oscillating frequency becomes an intermediate frequency of about 7 Hz, the influence of the inductance of the power supply circuit appears, and as shown in FIG. 2I, the maximum position I ₅ of the welding current value I is the oscillating position R with the maximum oscillating width. Both are in phase with a delay relative to _{0 in} the case of a low frequency of 5 Hz. Therefore, when the same figure (B) and the same figure (I) are combined and the component of the time t is eliminated, the locus of the welding current with respect to the oscillating position almost coincides with the oscillating reciprocation as shown in the same figure (E). . When the positional deviation occurs, the welding current locus becomes as shown in FIGS. 8 (A) and 8 (C) described above.

Further, when the oscillating frequency becomes a high frequency of about 10 Hz, the influence of the inductance of the power supply circuit becomes large, and the maximum position I ₅ of the welding current value I is further delayed than the case of 7 Hz with respect to the oscillating position R _{0 having the} maximum oscillating width. Then, as shown in FIG. 7J, the maximum position I ₅ of the welding current value is a position (position delayed) by Θ _{2 with} respect to the maximum position R ₀ of the oscillating width at the right end. . Therefore, when (B) and (J) in the same figure are combined and the component at time t is deleted, the locus of the welding current with respect to the oscillating position is as shown in FIG. The rotation direction (reverse rotation) is opposite to that in the case of D).

Fig. 11 shows the circuit inductance of welding power source [mH] (horizontal axis).
2 is a graph showing the relationship between the oscillating frequency [Hz] (vertical axis) and In the figure, for example, when the circuit inductance is 0.25 [mH], the welding current locus is in reverse rotation, the oscillation frequency is 6.5 [Hz], whereas when the circuit inductance increases to 1.0 [mH], the reverse occurs. It shows that the oscillating frequency for rotation drops to 3.0 [Hz].

(2) Embodiment of claim 2 In the structure of claim 1, the oscillation frequency is 2
The positional deviation between the center of the oscillate and the welding line is detected by utilizing the fact that the locus of the welding current varies depending on the oscillating direction from the low frequency of -5 Hz to the high frequency of 7-10 Hz. Therefore, when the oscillating frequency becomes an ultra-low frequency of less than 2 Hz, the arc length maintains a constant value and the welding current value does not differ depending on the oscillating direction, so it becomes impossible to detect the positional deviation between the oscillating center and the welding line. .

Therefore, the second claim is a conventional low frequency oscillating technique that does not cause a difference in the locus of welding current depending on the oscillating direction and a range of low frequency to high frequency that causes a difference in the locus of welding current depending on the oscillating direction. In combination with the technique of the first term, a welding line tracing control method that can be shared from ultra-low speed to high frequency is provided.

Example 6 The sixth example is the first example with respect to the second claim, in which the welding torch WT is oscillated to detect the change in the welding current due to the change in the arc length and the wire protrusion length. , In the welding line tracing control method of causing the welding torch to follow the welding line W ₀ by the detection signal, the welding current value Re (first value) detected at the right end of the oscillation when the welding torch is traveling to the right of the oscillation width. (Detection signal) and welding current value Cl detected at the center of the oscillating head while traveling to the left (second
The first comparison signal R ₆ of Re / Cl, which is the ratio of the ratio of the welding current of the welding torch and the welding current value Le detected at the left end of the oscillation when the welding torch is moving to the left of the oscillation width. Ratio of (third detection signal) to welding current value Cr (fourth detection signal) detected at the oscillating center when traveling to the right
The second comparison signal L ₆ of Le / Cr is calculated, and the signal J of these differences is calculated.
₆ = R ₆ -L ₆ are weld line scanning control method of moving the oscillating center of the welding torch in the direction of decrease. In order to improve the detection accuracy described above, the first and second comparison signals are R ₆ = Re / Cl and L ₆ = Le / Cr at low frequencies, and R ₆ = Re at high frequencies. / Cr and L ₆ = may be switched to the Le / Cl.

An embodiment in which the oscillating frequency can be shared from a very low frequency of 0.5 to 2 Hz to a high frequency of 7 to 10 Hz is shown in FIGS.
This will be described using the figure.

Ultra Low Frequency Oscillation In FIG. 6 (A), since R ₆ = Re / Cl> 1 and L ₆ = Le / Cr <1, R ₆ −L ₆ > 0. It is the same. In the figure (C), R ₆ = Re / Cl <1, L ₆ = Le /
Since Cr> 1, R ₆ −L ₆ <0, and the same as in the first embodiment.

Low Frequency and Intermediate Frequency Oscillation In FIG. 7 (A), R ₆ = Re / Cl> 1 and L ₆ = Le / Cr <1, so R ₆ −L ₆ > 0. Similar to the example. In the figure (C), R ₆ = Re / Cl <1, L ₆ = Le /
Since Cr> 1, R ₆ −L ₆ <0, and the same as in the first embodiment.

In FIGS. 8A and 8C, L ₆ ≈1, respectively.
R ₆ ≈1, but the same as above.

High frequency oscillation In FIG. 9 (A), R ₆ = Re / Cl> 1 and L ₆ = Le / Cr≈1, so R ₆ −L ₆ > 0, and the same as in the case of FIG. Become. In the figure (C), R ₆ = Re / Cl≈1, L ₆ = Le /
Since Cr> 1, R ₆ −L ₆ <0, and the same applies to the case of FIG. 7 below. In case of high frequency oscillation, Cr
By switching between Cl and Cl, the Re / Cr ratio and the Le / Cl ratio become larger than the Re / Cl ratio and the Le / Cr ratio, so that the accuracy can be improved.

Seventh Embodiment A seventh embodiment is a second embodiment with respect to the second claim, and in the sixth embodiment, the difference (Re− between the first detection signal Re and the second detection signal Cl). Cl), and then the difference (Le-Cr) between the third detection signal Le and the fourth detection signal Cr, and the signal J ₇ = R ₇ -L _{7 of} these differences becomes the minimum value. As described above, the welding line tracing control method is to move the oscillating center of the welding torch.

In order to improve the detection accuracy described above, the first and second
The comparison signal of R ₇ = Re-Cl and L ₇ = Le-Cr at low frequency
Then, at high frequencies, R ₇ = Re-Cr and L ₇ = Le-Cl may be switched.

Similar to the sixth embodiment, description will be made with reference to FIGS. 6 to 9.

Ultra low frequency oscillation In FIG. 6 (A), R ₇ = Re-Cl> 0, L ₇ = Le-Cr <0,
R ₇ −L ₇ > 0, which is the same as in the first embodiment.
In FIG. _{(C), R 7 = Re} -Cl <0, L 7 = Le-Cr> 0, R 7
-L ₇ <0, which is the same as in the first embodiment.

Low-frequency and intermediate-frequency oscillation In FIG. 7 (A), R ₇ = Re-Cl> 0, L ₇ = Le-Cr <0,
R ₇ −L ₇ > 0, which is the same as in the first embodiment.
In FIG. _{(C), R 7 = Re} -Cl <0, L 7 = Le-Cr> 0, R 7
-L ₇ <0, which is the same as in the first embodiment.

In FIGS. 8A and 8C, L ₆ ≈0,
R ₆ ≈0, but the same as above.

In the high frequency oscillating Figure _{9, R 7 = Re-Cl>} 0, L 7 = Le-Cr ≒ 0, R 7 -L 7
> 0, and thereafter the same as in the case of FIG. In FIG. _{(C), R 7 = Re} -Cl ≒ 0, L 7 = Le-Cr> 0, R 7 -L 7
<0, which is the same as the case shown in FIG. In addition,
In the case of high frequency oscillating, by switching between Cl and Cr, the difference of Re-Cr and the difference of Le-
Since the difference in −Cl can be increased, the accuracy can be improved.

(3) Apparatus for carrying out the control method of the present invention Fig. 14 is a schematic configuration diagram of the entire apparatus for arc welding by applying the control method of the present invention.

FIG. 1 (A) shows a block of an embodiment of an apparatus for carrying out the welding line copying control method according to the first and second claims.

In FIG. 1, 1 is a welding robot main body, WT is a welding torch attached to the wrist of the welding robot, W is a consumable electrode, Wa is a consumable electrode tip, and We and Wr are a left-side welded object and a right-side welded object, respectively. The weld line W ₀ is formed by the butting line of the two. A welding power source 9 is connected between the welding torch WT and the object to be welded through a welding current detection circuit 10. Reference numeral 8 denotes a welding torch position control circuit for the robot, which controls the movement of the welding torch WT and the oscillating operation in the directions of the arrows L ₀ and R ₀ , and receives the output signal of the encoder for detecting the position of the welding torch WT as an input. The torch position pulse train signal S ₈ is output. Reference numeral ₁₁ is a welding torch position detection circuit which receives the torch position pulse train signal S ₈ and outputs the oscillating position detection signal S ₁₁ shown in FIG. 1 (B). 1
Reference numeral 8 denotes an oscillating memory circuit that sequentially stores the oscillating position detection signal S ₁₁ . 19 is a memory circuit for oscillation
It is a filter circuit for oscillating that reads out a signal for N cycles of oscillating before the latest signal from 18 and removes low frequency noise and drift. 20 is a welding current detection circuit 10
Is a welding current storage circuit that sequentially stores a signal S ₁₀ corresponding to the welding current detected by the. Reference numeral 12 denotes a current corresponding to the welding current I shown in FIG. 1 (C) by reading a signal for N cycles of an oscillating cycle prior to the latest signal corresponding to each oscillating position and removing high frequency noise. It is a welding current filter circuit that outputs a filter signal S ₁₂ . 13 is the position filter signal S ₁₉ and the current filter signal S ₁₂
2 is a position / current waveform synthesizing circuit which outputs a waveform signal S ₁₃ indicating a change in welding current with respect to the oscillating position shown in FIG. 1 (D). 14 is a welding current detection signal (first detection signal) detected when the right half of the oscillating width is traveling to the right (hereinafter referred to as right traveling) by inputting the waveform signal S ₁₃ and traveling to the left. When doing (below,
It is a right position current difference calculation circuit that compares a welding current detection signal (second detection signal) detected when moving to the left) and outputs a first comparison signal R shown in FIG. 1 (E). Reference numeral 15 denotes a welding current detection signal (third detection signal) detected when the left half of the oscillating width is detected when moving leftward and a welding current detection signal (fourth detection signal) detected when moving rightward with the waveform signal S ₁₃ as an input. It is a left position current difference calculation circuit which compares and outputs the second comparison signal L shown in FIG. 1 (F). Reference numeral 16 is a left-right current difference calculation circuit that outputs a left-right current signal J = RL of the difference between the first comparison signal R and the second comparison signal L. Reference numeral 26 denotes a position deviation calculation circuit that receives a left-right current difference signal J and outputs a signal (hereinafter, referred to as a position deviation signal) Z indicating a deviation direction and a deviation amount of a welding line center position from a function F (J). is there. Reference numeral 17 denotes an oscillating center position correction circuit which receives the position shift signal Z and calculates a scanning operation amount Q. 25 is the copy operation amount Q
Is a communication driver that outputs a center position correction signal S ₁₇ for correcting the oscillating center position to the welding torch position control circuit 8 of the robot described above.

In FIG. 14, description of the same symbols as in FIG. 1 is omitted. In the figure, reference numeral 2 is a robot control device, which includes the welding torch position detection circuit 11 and the torch position control circuit 8 of FIG. 1 (A). Reference numeral 3 denotes a copying control device, which includes the circuits 12 to 26 described in FIG. 1 (A). Reference numeral 21 denotes an encoder signal accumulation counter which forms a part of the torch position detection circuit 11, and accumulates encoder signals corresponding to the oscillating position to accumulate the encoder signal.
The count value of 21 is read into the CPU described later. Reference numeral 12 denotes a CPU, which is the reference numeral 12 to 17, 19 and 26 described in FIG. 1 (A).
Each circuit of is formed. Reference numeral 24 is a main memory circuit, and forms circuits 18 and 20 in FIG. 1A in a part of the area. Reference numeral 10 is a welding current detection circuit, which includes a current detection Hall element 10a, an amplification circuit 10b, and a sampling hold circuit 10c.
And an A / D converter 10d.

The above-described right position current difference calculation circuit 14 and left position current difference calculation circuit 15 perform the following calculations in each of the above-described embodiments.

First Embodiment The arithmetic circuit 14 receives the waveform signal S ₁₃ as an input, and detects an integrated value ΣRr (first detection signal) of welding current detected by the welding torch in the right half of the oscillating width when traveling to the right and when traveling to the left. Ratio of integrated welding current ΣRl (second detection signal) to ΣRr / ΣRl
The first comparison signal R ₁ of

The calculation circuit 15 receives the waveform signal S ₁₃ as an input and integrates the welding current integrated value ΣLl (third detection signal) detected when the left half of the oscillating width of the welding torch is moved leftward and the welding current detected when moved rightward. Ratio of value ΣLr (fourth detection signal) ΣLl / ΣLr
The second comparison signal L ₁ of

Second Embodiment The arithmetic circuit 14 in the first embodiment has a first difference (ΣRr−ΣRl) between the first detection signal ΣRr and the second detection signal ΣRl.
And outputs the comparison signal R ₂ . In the first embodiment, the arithmetic circuit 15 outputs the _second comparison signal L ₂ which is the difference (ΣLl−ΣLr) between the third detection signal ΣLl and the fourth detection signal ΣLr.

Third Embodiment The arithmetic circuit 14 receives a waveform signal S ₁₃ as an input and a welding current signal Rr (first detection signal) detected by the welding torch at an intermediate position when moving to the right half of the oscillating width and a leftward movement. Ratio Rr with the welding current signal Rl (second detection signal) detected at the intermediate position during
Output the first comparison signal R ₃ of / Rl. The arithmetic circuit 15 receives the waveform signal S ₁₃ as input and detects the welding current signal Ll (third detection signal) detected by the welding torch in the left half of the oscillating width at the intermediate position when moving to the left and at the intermediate position when moving to the right. A second comparison signal L ₃ having a ratio Ll / Lr with the welding current signal Lr (fourth detection signal) is output.

Fourth Embodiment The arithmetic circuit 14 in the third embodiment is the same as the first detection signal.
Outputs the Rr and first comparison signal R ₄ of the difference between the second detection signal Rl (Rr-Rl). In the third embodiment, the arithmetic circuit 15 uses the difference (Ll−−) between the third detection signal Ll and the fourth detection signal Lr.
Lr) second comparison signal L ₄ is output.

Fifth Embodiment In the fifth embodiment, the polarities of the first comparison signal R and the second comparison signal L are changed when the oscillation frequency is a high frequency of 7 to 10 Hz in the first to fourth embodiments. This is the case when they are reversed.

Sixth Embodiment The arithmetic circuit 14 receives the waveform signal S ₁₃ as an input and detects the welding current value Re (first detection signal) detected at the right end of the oscillation to the right of the welding torch and the center of the oscillation when moving to the left. The first comparison signal R ₆ having the ratio Re / Cl with the welding current value Cl (second detection signal) is output. The arithmetic circuit 15 receives the waveform signal S ₁₃ as an input, the welding current value Le (third detection signal) detected at the left end of the oscillation when the welding torch moves left, and the welding current value Cr detected at the center of the oscillation when moving right. The second comparison signal L ₆ having the ratio Le / Cr with the (fourth detection signal) is output. In the case of high frequency oscillation, Re / Cr may be output as the first comparison signal R ₆ and the second comparison signal Le / Cl may be output in order to improve the detection accuracy described above. .

Seventh Embodiment The arithmetic circuit 14 is the same as the sixth embodiment in the first detection signal.
Outputting a first comparison signal R ₇ of Re and the difference between the second detection signal Cl (Re-Cl). In the sixth embodiment, the arithmetic circuit 15 has a difference (Le−) between the third detection signal Le and the fourth detection signal Cr.
The second comparison signal L ₇ of Cr) is output. In order to improve the detection accuracy described above, in the case of high frequency oscillation,
(Re-Cr) may be output as the first comparison signal R _{7 and} (Le-Cl) may be output as the second comparison signal.

Other Modifications The copying control method of the present invention is not limited to the above-described embodiments, and various modifications included in the claims, such as changes in the arc length and the wire protrusion length by oscillating the welding torch. For electrical changes, the average value of welding current, digital signal of sampled welding current, voltage or current during arc period or short circuit period of short arc welding, current or voltage during base period of pulse arc, etc. may be used. it can.

(4) Explanation of Sampling Operation The sampling operation of the copying control device 3 shown in FIGS. 1 and 14 will be described.

Sampling cycle of torch position and welding current The frequency Fs of the clock signal that determines the sampling frequency of the data of each oscillating position of the welding torch WT and the data of the welding current value corresponding to each oscillating position is A high frequency of 10 to 15 KHz is selected to enable accurate sampling of minute changes in the welding current waveform when the pulse current and base current change in pulse arc welding.

Oscillation center position correction cycle If the oscillation center position correction cycle (hereinafter referred to as the position correction cycle) Td is shortened, it is possible to finely control the positional deviation between the welding torch and the welding line.
Td cannot be made shorter than the one-time position correction calculation time Tc. On the contrary, if the position correction cycle Td is lengthened, the calculation time for the scanning control can be lengthened, so that the number of data that can be processed in one oscillation center position correction can be increased and the reliability is improved. be able to.

Therefore, if the position correction cycle Td is the distance Ld that the welding torch moves in the welding line direction during the position correction cycle Td, the moving speed of the welding torch in the welding line direction (welding speed)
With respect to the set value of Vd, a value is selected in which the moving distance Ld is substantially constant and the position correction cycle Td is longer than one position correction calculation time Tc. That is, for Td, the maximum value of either Ld / Vd or Tc may be selected.

Memory of welding torch position and welding current detection signal Welding torch position detection signal S ₁₁ and welding current detection signal S
₁₀ is stored in a buffer that fills a part of the area of the main memory circuit 24. The buffer used here is information about which position in the buffer the data next to the last address of the buffer will be written to (read out from) the ring buffers 18a and 20a (hereinafter referred to as the ring buffer pointer). That is, writing and reading are performed.

FIG. 15 is a flow chart of the sampling operation. In FIG. 15, the oscillation position detection signal S ₁₁ and the welding current detection signal S ₁₀ are sampled and the ring buffers 18a and 20 are sampled.
The flowchart of the sampling operation written in a is shown.

When the power is turned on, the memory circuit for oscillation 18 and the memory circuit for welding current 20 are initialized.

At the start of the scanning control, a clock counter (not shown) for the detection signal sampling clock signal is reset.

The sampling clock signal is started at the same time when the copying control is started.

The encoder signal detected by the encoder of the torch position detection circuit 11 is accumulated by the encoder signal accumulation counter 21 and a series of oscillated position detection signals S ₁₁ are read into the CPU.

The series of oscillating position detection signals S ₁₁ shown in FIG. 16 (A) read by the CPU is stored in the oscillating ring buffer 18a of the main memory circuit 24 at the position indicated by the ring buffer pointer.

The welding current detection signal S ₁₀ of the welding current detection circuit 10
Convert it to a digital signal with the A / D converter 10d shown in the figure.
Read to CPU.

A series of welding current detection signal S ₁₀ shown in FIG. 17 I read the CPU (A), the welding current ring buffer 20a in the main storage circuit 24 stores the position where the ring buffer pointer is indicated.

The ring buffer pointer is advanced, the clock counter not shown in FIGS. 1 and 14 is incremented by 1, and sampling is repeated until the count value of the clock counter reaches the set value M. (The set value M is, for example, the product of the frequency Fs of the sampling clock signal and the position correction cycle Td.) When the clock counter value reaches M, the clock counter is reset and the scanning control calculation is started. Sampling is repeated after the command is output.

When the sampling is not continued, the sampling clock signal is stopped and the scanning control is ended.

(5) Description of filter operation Oscillation filter A series of oscillation position detection signals S shown in Fig. 16 (A).
_The oscillator ring buffer 18a storing ₁₁ stores a series of oscillating position signals (hereinafter referred to as data) of oscillating N cycles (for example, 1 cycle) before the latest oscillating position detection signal S ₁₁ instructed by the ring buffer pointer.
Xm) is read and stored in the oscillation buffer 18b (see FIG. 16B).

The data Xm stored in the oscillation buffer 18b is
It outputs to the oscillating filter circuit 19 to remove low frequency noise and drift, and outputs the position filter signal S ₁₉ (hereinafter referred to as data X) shown in FIG. 16 (C).

From the welding current ring buffer 20a for storing welding current detection signal S ₁₀ shown in welding current filter 17 view (A), oscillating N cycles before the latest current signal S ₂₀₁ to the ring buffer pointer is commanded A series of welding current signals (for example, one cycle) (hereinafter referred to as data Ym) is read out and stored in the welding current buffer 20b (see FIG. 17 (B)).

The stored data Ym to the welding current buffer 20b, and outputs the welding current filter circuit 12 removes high-frequency noise, the current filter signal S ₁₂ shown in Figure No. 17 (C) (hereinafter, referred to as data Y) output To do.

Description of Operation of Oscillating Filter Circuit The operation of the oscillating filter circuit 19 will be described with reference to FIGS. 18 (A) to (D).

As shown in FIG. 7A, the oscillation buffer 18b
The first signal value and the last (latest) signal value S _{111 of} the data Xm read out from are connected by a straight line, and the straight line is converted as shown in FIG.

Further, the average value Xa (the same figure (C)) of the maximum value Xl and the minimum value Xs of the data of the same figure (B) is converted as shown in the same figure (D) so that it becomes the zero point of the oscillating position.

Operating Principle of Welding Current Filter Circuit The solid line in FIG. 19 shows the time course t of a series of current buffer signals S ₂₀ (data Ym) of the welding current ring buffer circuit 20a. In the figure, the smoothing time Ta (10
Calculate a moving average of U data in the range of 50 msec.

The moving average number U at this time is the product of the smoothing time Ta of the buffer signal and the sampling clock signal frequency Fs, and the moving average value Yt at time T ₁ is represented by the following equation, and FIG. It becomes like the dotted line.

(6) Calculation of position correction signal The position / current waveform is calculated by using the position filter signal S ₁₉ (data X) shown in FIG. 16 (C) and the current filter signal S ₁₂ (data Y) shown in FIG. 17 (C). Input to synthesis circuit 13
The waveform signal S ₁₃ shown in FIG. 20 is formed.

The right position current difference calculation circuit 14 receives the waveform signal S ₁₃ as an input, and the sum Σ of the digital values of the current data when the welding torch shown in FIG. 21 (B) moves rightward in the right half of the oscillation width.
The first comparison signal R ₈ = ΣRr−ΣRl, which is the difference between Rr and the total sum ΣRl of the digital values of the current data when moving leftward in the right half shown in FIG. See A)).

21 (A) to (C) and 22 (A) to (C), the horizontal axis represents the position filter signal S ₁₉ corresponding to the oscillating position P, and the vertical axis represents the welding current value I. It represents the current filter signal S ₁₂ .

The left position current difference calculation circuit 15 receives the waveform signal S ₁₃ as an input, and the sum Σ of the digital values of the current data when the welding torch shown in FIG. 22 (B) moves leftward in the left half of the oscillation width.
The second comparison signal which is the difference between Ll and the sum ΣLr of the digital values of the current data when the left half shown in FIG.
L ₈ = ΣLl−ΣLr is calculated (see FIG. 22 (A)).

Left and right current difference calculating circuit 16 calculates the first comparison signal R ₈ a signal J = R ₈ -L ₈ of the difference between the second comparison signal L _8.

The position shift calculation circuit 26 outputs a signal Z = F (J) representing the direction and amount of the welding line center position shift from the function F (J) having the difference signal J as a variable.

For example, aJ + b is used as the function F (J).

However, a and b are predetermined constants. For example, when the oscillating frequency is 5 [Hz], the waveform signal S ₁₃ is in the positive rotation direction of “8”, so that a> 0. Also 10 [H
In the case of [z], the rotation direction is reverse, so a <0.

Calculation of misalignment signal Z When the tip Wa of the consumable electrode is shifted in advance from the welding line W ₀ by a known value Zr and welding is performed, and the signal Jr of the difference in the above-mentioned item is calculated, the groove shape, the welding torch posture, etc. are calculated. , The state diagrams shown in FIGS. 23 (A) and (B) are obtained.

As a result, for example, in FIG. 23 (A), Zr and Jr are substantially linear and can be replaced with the Zr = aJr + b equation, and when the values of a and b are obtained by regression analysis, The oscillating center position shift data Z can be obtained from the signal J of the difference between the terms.

Reference numeral 17 denotes an oscillating center position correction circuit that obtains the scanning operation amount Q from the position shift signal Z. For example, in the PID control, the scanning operation amount Q is However, k, l, and m are constants, and i is the number of times of scanning control calculation.

The communication driver 25, which receives the scanning operation amount Q, outputs the center position correction signal S ₁₇ to the torch position control circuit 8 to correct the oscillating center position deviation, thereby performing the copying control.

[Effects of the Invention] The effects of the present invention are as follows.

(1) The welding line can be traced in high-speed welding.

In the conventional welding line copying control method, the oscillating frequency is 5H.
Weld lines could only be detected up to an intermediate frequency of about z. FIG. 12 is a diagram showing a standard deviation [mm] (vertical axis) of a positional deviation detection error (hereinafter referred to as a detection error) with respect to a welding line with respect to an oscillation frequency [Hz] (horizontal axis). The dotted line in the figure is a curve showing the standard difference in detection error of the conventional control method, and when the oscillating frequency is 6 Hz or higher,
It could not be used because the standard deviation of the detection error greatly exceeded 1 [mm]. On the other hand, the solid line in the figure is a curve showing the standard deviation of the detection error of the control method of the present invention, and the standard deviation of the detection error is at the on-rate frequency of 2 to 6 Hz.
It is less than 1.0 [mm], and when it exceeds 6 Hz, the standard deviation of the detection error decreases, which is the opposite of the conventional method.
m], and the detection error is small especially at high frequencies.

In the conventional copying control method, if the welding speed is increased without increasing the oscillation frequency, the meandering of the welding bead due to the oscillation becomes conspicuous. Therefore, the maximum welding speed when following the conventional welding line is 120 [cm /
min] and about 80 [cm / min] in overlap fillet welding. On the other hand, in the present invention, since the oscillating frequency can be set to a high frequency of 7 to 10 Hz, the maximum welding speed when following the welding line is 200 [cm / min] for downward fillet welding and 150 [for overlapping fillet welding. cm / min]. That is, even if the welding speed is doubled from the conventional one, the oscillating frequency can be doubled from the conventional one.

In addition, in the past, the maximum welding speed when following the welding line had the above-mentioned limit, so it was not possible to increase the welding speed even for thin plates, so the minimum plate thickness is 2.0 [mm] for horizontal fillet welding. For lap fillet welding, the limit was 3.2 [mm]. On the other hand, in the present invention, the minimum plate thickness can be applied to 1.2 [mm] in horizontal fillet welding and to 2.3 [mm] in lap fillet welding.

(2) The accuracy of following the welding line is improved.

The arc sensor detects the displacement from the welding line based on the average current data of the welding current in one cycle or half cycle of oscillating, but it can be detected in a unit time by increasing the oscillating frequency. The number of times increases.

Figure 13 shows the welding line taught (coincident with the horizontal axis),
It shows the positional deviation of the actual welding line Ws arranged at an angle, where the horizontal axis is the welding time [sec] and the vertical axis is the actual welding that is inclined with respect to the taught welding line (coincident with the horizontal axis). It is the displacement distance [mm] of the arrangement with the line. The dotted line in the figure is
The time lapse of the positional deviation between the inclined actual welding line Ws and the oscillating center C by the conventional control method with the oscillating frequency of 2.5 Hz is shown, and the maximum positional deviation is 1.0 [mm]. On the other hand, the solid line in the figure shows that the oscillation frequency is
Inclined actual weld line Ws according to the control method of the present invention at 10 Hz
Shows the time lapse of the positional deviation between the oscillating center C and the oscillating center C, and the maximum value of the positional deviation is 0.5 [mm] or less, which is less than half of the conventional value, and the accuracy of welding line tracking is improved.

(3) Copy control in vertical downward welding is possible.

In vertical down welding, the molten metal hangs below the arc, and the molten metal flows unsteadily to the surface of the groove. It was extremely difficult to carry out by control. On the other hand, in the control method of the present invention, since the oscillating frequency can be set to a high frequency to increase the welding speed, the welding torch (arc) is welded at a welding speed higher than the drooping speed of the molten metal. Since it is moved, it is possible to perform stable follow-up control of vertical downward welding without being affected by the dripping of molten metal. For example, the vertical corner of the welding speed of 200 [cm / min] It is possible to perform downward meat welding and vertical lap fillet welding with a welding speed of 150 [cm / min].

(4) High-precision copying control is possible even during small current welding.

In the copying control method using the arc sensor, the detection error becomes large when the welding current becomes small. However, in the copying control method of the present invention, even when the current becomes small, the detection error becomes larger than that in the conventional case by increasing the oscillation frequency. Since the size can be reduced, the copy control method can be performed even when welding with a small current as compared with the conventional method.

(5) Applicable to various welding methods.

In the conventional copying control method, since it was premised that the arc length was substantially constant, it could not be commonly used for the welding method in which the arc length fluctuates or the circuit inductance of the welding power source is different. On the other hand, since the copying control method of the present invention can be applied even if the arc length fluctuates or the circuit inductance of the welding power source changes, spray arc, short arc, or pulse arc can be used for wide welding conditions. It can be used alone or in combination over a range.

[Brief description of drawings]

FIG. 1 (A) is a block diagram of an embodiment of an apparatus for carrying out the welding line copying control method of the present invention, and FIGS. 1 (B) to (E) are output waveform diagrams of each circuit. FIG. 7B is a waveform diagram of the oscillation position detection signal output from the welding torch position detection circuit 11, FIG. 6C is a waveform diagram of the welding current detection signal output from the filter circuit 12, and FIG. A waveform diagram of a waveform signal output from the current waveform synthesizing circuit 13, a waveform diagram of the first comparison signal output from the right position current difference calculation circuit 14 in the same diagram (E), and a left position current in the same diagram (F). 5 is a waveform diagram of a second comparison signal output from the difference calculation circuit 15. FIG. FIG. 2 is an explanatory diagram in the case where there is no positional deviation in the conventional copying control method and the arc length is assumed to be constant. FIG. 2A shows the relationship between the oscillating position and the welding current value. As shown in the figure, (B) shows the wire tip position Wa corresponding to the oscillating position of the welding torch WT and the wire protrusion lengths A ₁ and A _0.
The figure showing the relationship of the arc length B ₀ , and the figures (C) and (D) are figures showing the relationship between the welding current value I and the oscillating position P (vertical axis) with respect to the elapse of time t (horizontal axis), respectively. . FIG. 3 is a diagram showing the relationship between the oscillating position and the welding current value when there is a positional deviation in the conventional copying control method of FIG. FIG. 4 is a diagram showing a relationship between an actually measured oscillating position and a welding current value when the oscillating frequency is about 2 to 5 Hz and there is no displacement, and FIG. 5 shows the positional displacement in FIG. It is a figure which shows the relationship between the measured oscillating position and welding current value when there are few. FIGS. 6 to 9 show the relationship between the oscillating position and the welding current value obtained from the differential equation in consideration of the variation of the arc length and the inductance of the welding power source circuit for examining the control method of the present invention. FIGS. 6 (A) to 6 (C) show an ultra-low frequency of oscillating frequency of 0.5 to 2 Hz, and FIG.
Figures (A) to (C) are low frequencies of 2 to 5 Hz, Figure 8 (A)
9A to 9C show intermediate frequencies of 5 to 7 Hz, and FIGS. 9A to 9C show high frequency of 7 to 10 Hz. It is a figure which shows the relationship between an oscillating position and a welding current value in the case of not being present, and when shifting to the left. Fig. 10 (A) shows the welding center, oscillating center C and welding line.
When W ₀ matches a diagram showing the relationship between the position of the oscillating position and the weld object (when there is no positional deviation), FIG (B) is a diagram showing an oscillating position P over time t, (C) to (F) of the figure are diagrams showing the loci of changes in the welding current value I with respect to the oscillating position P when the oscillating frequencies are 0.5 Hz, 5 Hz, 7 Hz and 10 Hz, respectively (G) to (G). J) is a diagram showing a change in welding current value I with respect to time t. FIG. 11 is a graph showing the relationship between the circuit inductance [mH] of the welding power source (horizontal axis) and the oscillating frequency [Hz] (vertical axis). FIG. 12 is a diagram showing the standard deviation [mm] (vertical axis) of the positional deviation detection error from the welding line with respect to the oscillation frequency [Hz] (horizontal axis). Figure 13 shows the welding line taught (coincident with the horizontal axis),
Positional deviation distance [m] between the welding time [sec] (horizontal axis) and the actual welding line that is inclined to the taught welding line [m]
It is a diagram which shows the relationship with [m] (vertical axis). FIG. 14 is a schematic configuration diagram of an entire apparatus for performing arc welding by applying the copying control method of the present invention. FIG. 15 shows a flow chart of the sampling operation of the copying control apparatus. FIG. 16 (A) is a diagram showing a time course of a series of oscillating position detection signals S ₁₁ read in the oscillating ring buffer 18a. FIG. 16B is a diagram showing a time course of a series of oscillating position signals (data Xm) read in the oscillating buffer 18b. FIG. 16C is a diagram showing the time course of a series of filter signals S ₁₉ (data X) output from the oscillating filter circuit 19. FIG. 17 (A) is a diagram showing a time course of a series of welding current detection signals S ₁₀ read in the welding current ring buffer 20a. FIG. 17 (B) is a diagram showing a time course of a series of welding current detection signals (data Ym) read in the welding current buffer 20b. FIG. 17 (C) is a diagram showing a time course of a series of current filter signals S ₁₂ (data Y) output from the welding current filter circuit 12. FIGS. 18A to 18D show an oscillating filter circuit.
It is a waveform diagram explaining the operation sequence of 19. FIG. 19 is a view showing a time course of a series of buffer signals (data Y) of the welding current buffer circuit 20. FIG. 20 shows the waveform signal output from the left-right current difference calculation circuit 16.
It is a waveform diagram of S ₁₃ . 21 (A) to 21 (C) are waveform charts for explaining the operation of the right position current difference calculation circuit 14. 22 (A) to 22 (C) are waveform charts for explaining the operation of the left position current difference calculation circuit 15. 23 (A) and 23 (B) are diagrams for obtaining constants of a function for calculating the displacement of the oscillating center position. (See FIGS. 6 to 9) First comparison signal R ... ΣRr / ΣRl, ΣRr / ΣRl, Re / Rl, Rr
-Rl, Re / Cl, Re-Cl Second comparison signal L ... ΣLl / ΣLr, ΣLr / ΣLl, Ll / Lr, Ll
-Lr, Le / Cr, Le-Cr P ... Oscillating position I ... Welding current

Claims (2)

[Claims] 1. A welding torch is oscillated to detect electrical changes associated with changes in arc length and wire protrusion length,
In a welding line tracing control method for causing a welding torch to follow a welding line by the detection signal, in the left direction with the first detection signal detected when the welding torch is traveling rightward in the right half of the oscillating width. A first comparison signal for comparing with the detection signal detected while moving forward and the detection signal detected when the welding torch is moving leftward in the left half of the oscillating width A second comparison signal for comparing the detection signal detected when the welding torch is detected, and the center of the welding torch is moved in a direction in which the difference between the first comparison signal and the second comparison signal decreases. Welding line copying control method. 2. A welding line tracing control method for oscillating a welding torch to detect an electrical change associated with a change in arc length and wire protrusion length, and causing the welding torch to follow the welding line by the detection signal. A first comparison for comparing the detection signal detected at the right end of the oscillate when the welding torch is traveling to the right of the oscillating width with the detection signal detected at the oscillating center when traveling to the left. A second signal for comparing the signal and the detection signal detected at the left end of the oscillation when the welding torch is traveling to the left of the oscillating width with the detection signal detected at the center of the oscillation when traveling to the right. A welding line tracing control method for calculating a comparison signal and moving the oscillating center of the welding torch in a direction in which the difference between the first comparison signal and the second comparison signal becomes smaller.